1. Field of the Invention
The present invention relates to a leakage tester for detecting a leak in an airtight article, for example, an endoscope.
2. Description of the Related Art
For example, an endoscope is a reusable medical device and thus must always be washed and disinfected. In this regard, the presence of a pin hole or looseness of a connection in the endoscope causes the intrusion of a liquid such as water or disinfectant into the endoscope, which may cause a failure in an electric system such as an optical fiber or a CCD. Thus, in order to prevent such a situation, a leak test must be carried out on the endoscope.
A common leak test method for an airtight measurement object such as an endoscope includes immersing the measurement object into water, injecting pressurized air into the measurement object, and checking for the bubbles thus generated. However, this method requires a human operator to execute visual checks and thus fails to automate the leak test. As a result, a manual operation is constantly required.
In view of this, in order to automatically detect a leak in the measurement object, it is common to use a method of pressurizing the inner portion of the measurement object to seal the measurement object and detecting a variation in internal pressure to thereby determine whether or not there is leakage. Further, as an example of a high-accuracy automatic measurement method, Japanese Unexamined Patent Application Publication No. 4-221733 or Japanese Patent No. 3186438 discloses a technique of determining the presence/absence of leakage by detecting a pressure difference between the pressure of a gas inside the measurement object and the pressure of a pressurized gas supplied from a pressurized gas source by using a differential pressure sensor. Further, as an example of a simpler leak test method, Japanese Unexamined Patent Application Publication No. 5-220110 discloses a method of detecting the internal pressure of an endoscope using a gauge pressure sensor.
However, the problem with the above-described method using the differential pressure sensor as disclosed in Japanese Unexamined Patent Application Publication No. 4-221733 and Japanese Patent No. 3186438 is that, in addition to the high cost of the sensor, the method requires a complex wiring structure and also complex correction processing, which all add to the overall complexity of the system.
Further, the above-described method using a gauge sensor as disclosed in Japanese Unexamined Patent Application Publication No. 5-220110 requires a pressure sensor having a full scale for a pressure equal to or higher than that used for the pressurization, thus leading to a problem in that the measurement must be performed for a long period of time in order to ensure accuracy when the changes in pressure due to leakage are minute.
The present invention has been made in view of the above-mentioned problems and provides an inexpensive and compact leakage tester capable of determining a leak in a measurement object automatically and with accuracy.